U.S. patent number 6,627,328 [Application Number 09/950,737] was granted by the patent office on 2003-09-30 for light-transmissive epoxy resin composition and semiconductor device.
This patent grant is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Eiichi Asano, Tsuyoshi Honda, Tatsuya Kanamaru, Toshio Shiobara.
United States Patent |
6,627,328 |
Kanamaru , et al. |
September 30, 2003 |
Light-transmissive epoxy resin composition and semiconductor
device
Abstract
An epoxy resin composition comprising (A) an epoxy resin, (B) a
curing accelerator, and (C) an inorganic filler is light
transmissive when it satisfies formulae (1) and (2): wherein
n.sub.A is the refractive index at T.sub.1.degree. C. of the cured
unfilled composition, n.sub.C is the refractive index at
T.sub.1.degree. C. of the inorganic filler, f.sub.A is a
temperature coefficient of the refractive index of the cured
unfilled composition, and f.sub.C is a temperature coefficient of
the refractive index of the inorganic filler. The cured composition
has improved heat resistance, humidity resistance and low stress as
well as high transparency over a wide temperature range. The
composition is suited for the sealing of optical semiconductor
devices.
Inventors: |
Kanamaru; Tatsuya (Gunma-ken,
JP), Honda; Tsuyoshi (Gunma-ken, JP),
Asano; Eiichi (Gunma-ken, JP), Shiobara; Toshio
(Gunma-ken, JP) |
Assignee: |
Shin-Etsu Chemical Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
18762739 |
Appl.
No.: |
09/950,737 |
Filed: |
September 13, 2001 |
Foreign Application Priority Data
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Sep 13, 2000 [JP] |
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2000-277405 |
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Current U.S.
Class: |
428/620; 257/789;
257/793; 257/795; 523/457; 523/458; 523/459; 523/466 |
Current CPC
Class: |
C08L
63/00 (20130101); Y10T 428/31511 (20150401); Y10T
428/12528 (20150115) |
Current International
Class: |
C08L
63/00 (20060101); H01L 029/12 () |
Field of
Search: |
;428/620
;523/457,458,459,466 ;257/789,793,795 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A3279210 |
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Dec 1991 |
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JP |
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A524882 |
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Feb 1993 |
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JP |
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Primary Examiner: Dawson; Robert
Assistant Examiner: Aylward; D.
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Claims
What is claimed is:
1. A light-transmissive epoxy resin composition comprising (A) an
epoxy resin, (B) a curing accelerator, and (C) an inorganic filler,
wherein said composition satisfies both the relationships of the
following formulae (1) and (2):
wherein n.sub.A is the refractive index at T.sub.1.degree. C. of
the cured product of the composition excluding the inorganic
filler, n.sub.C is the refractive index at T.sub.1.degree. C. of
the inorganic filler, f.sub.A is a temperature coefficient of the
refractive index of the cured product of the composition excluding
the inorganic filler, f.sub.C is a temperature coefficient of the
refractive index of the inorganic filler, and the temperature
coefficient of refractive index is given by the formula (3):
wherein n(T.sub.1) is the refractive index at T.sub.1.degree. C.
and n(T.sub.2) is the refractive index at T.sub.2.degree. C., with
the proviso that T.sub.1 <T.sub.2.
2. The epoxy resin composition of claim 1 wherein T.sub.1 is 10 to
50.degree. C., and T.sub.2 is 60 to 120.degree. C.
3. The epoxy resin composition of claim 1 wherein component (A) is
an epoxy resin having at least one naphthalene ring in a
molecule.
4. The epoxy resin composition of claim 1 wherein component (A) is
a mixture of an epoxy resin of the following general formula (4)
and an epoxy resin of the following general formula (5):
##STR8##
wherein R.sup.1 is a group represented by ##STR9## R.sup.2 is
independently hydrogen or an alkyl group of 1 to 6 carbon atoms,
R.sup.3 is hydrogen or a group represented by ##STR10## OG is
##STR11## k is 1 or 2, m is an integer of 0 to 2, and n is an
integer inclusive of 0.
5. The epoxy resin composition of claim 1 wherein component (A) is
an epoxy resin of the following general formula (6): ##STR12##
wherein n is an integer inclusive of 0.
6. The epoxy resin composition of claim 1 wherein inorganic filler
(C) is an amorphous silica-titania co-melt.
7. The epoxy resin composition of claim 1 further comprising (D) an
acid anhydride curing agent.
8. A semiconductor device sealed with the epoxy resin composition
of claim 1 in a cured state.
9. The light-transmissive epoxy resin composition of claim 1,
wherein the standard deviation of the refractive index give by
formula (1) is from 0 to 2.2.times.10.sup.-3.
10. The light-transmissive epoxy resin composition of claim 1,
wherein the standard deviation of the refractive index give by
formula (1) is from 0 to 0.8.times.10.sup.-3.
11. The light-transmissive epoxy resin composition of claim 1,
wherein the standard deviation of the temperature coefficient of
the refractive index give by formula (2) is from 0 to
0.9.times.10.sup.-5.
12. The light-transmissive epoxy resin composition of claim 1,
wherein the standard deviation of the temperature coefficient of
the refractive index give by formula (2) is from 0 to
0.2.times.10.sup.-5.
13. The light-transmissive epoxy resin composition of claim 1,
wherein component (B) is a combination of an acid anhydride curing
agent with an imidazole compound or an organophosphine
compound.
14. The light-transmissive epoxy resin composition of claim 1,
wherein component (C) comprises a member selected from the group
consisting of crystalline or amorphous silica, talc, mica, silicon
nitride, boron nitride, and alumina.
15. The light-transmissive epoxy resin composition of claim 7,
wherein component (D) is selected from the group consisting of
aliphatic acid anhydrides and alicyclic acid anhydrides.
Description
This invention relates to epoxy resin compositions of inorganic
filler loading type suitable as a sealing material for optical
semiconductor and affording cured products having high transparency
in various temperature environments, and semiconductor devices
sealed with the compositions in a cured state.
BACKGROUND OF THE INVENTION
While the recent advance of the information technology requires
effective transmission and processing of a vast quantity of
information bits, what is now under investigation as a substitute
for conventional signal transmission through electrical wiring is
semiconductor devices which take advantage of the high speed, low
loss, non-induction and other desirable features of optical signals
and mounting technology used therefor.
Most of prior art opto-functional devices are sealed with epoxy
resins which are free of inorganic filler in order that the resin
layer be transparent. Such unfilled epoxy resins are not
satisfactory when the heat resistance, humidity resistance and low
stress property of cured parts are taken into account. There is a
need for a transparent sealant which contains an inorganic
filler.
SUMMARY OF THE INVENTION
An object of the invention is to provide a light-transmissive epoxy
resin composition of inorganic filler loading type which is
suitable as a sealing material for optical semiconductor and
affords cured products maintaining high transparency in various
temperature environments. Another object is to provide a
semiconductor device sealed with the epoxy resin composition.
It has been found that when an epoxy resin composition comprising
an epoxy resin, a curing accelerator, and an inorganic filler as
essential components satisfies both the relationships of the
following formulae (1) and (2), cured products thereof maintain
high transparency in varying temperature environments.
Accordingly, the invention provides a light-transmissive epoxy
resin composition comprising (A) an epoxy resin, (B) a curing
accelerator, and (C) an inorganic filler, wherein the composition
satisfies both the relationships of the following formulae (1) and
(2).
Herein n.sub.A is the refractive index at T.sub.1.degree. C. of the
cured product of the composition excluding the inorganic filler,
n.sub.C is the refractive index at T.sub.1.degree. C. of the
inorganic filler, f.sub.A is a temperature coefficient of the
refractive index of the cured product of the composition excluding
the inorganic filler, f.sub.C is a temperature coefficient of the
refractive index of the inorganic filler, and the temperature
coefficient of refractive index is given by the formula (3):
wherein n(T.sub.1) is the refractive index at T.sub.1.degree. C.
and n(T.sub.2) is the refractive index at T.sub.2.degree. C., with
the proviso that T.sub.1 <T.sub.2.
Also provided is a semiconductor device sealed with the epoxy resin
composition in a cured state.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically illustrates the measurement of refractive
index and transmittance of a sample.
FIG. 2 is a schematic cross-sectional view of a semiconductor
device to which the invention is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The light-transmissive epoxy resin composition of the invention
includes (A) an epoxy resin, (B) a curing accelerator, and (C) an
inorganic filler as essential components and optionally, a curing
agent and other components. The type and amount of these components
are selected such that the composition may satisfy both the
relationships of the formulae (1) and (2).
In formula (1), n.sub.A is the refractive index at temperature
T.sub.1.degree. C. of the cured product of the composition
excluding the inorganic filler, and n.sub.C is the refractive index
at temperature T.sub.1.degree. C. of the inorganic filler. Formula
(1) means that the standard deviation of the refractive index of
the cured product of the unfilled composition on the basis of the
refractive index of the inorganic filler is less than
3.0.times.10.sup.-3. For the sake of brevity, the term "filled
composition" is used to denote an epoxy resin composition
comprising an epoxy resin, a curing accelerator, and an inorganic
filler, and "unfilled composition" used to denote an epoxy resin
composition comprising an epoxy resin and a curing accelerator, but
excluding an inorganic filler.
In formula (2), f.sub.A is a temperature coefficient of the
refractive index of the cured product of the unfilled composition,
and f.sub.C is a temperature coefficient of the refractive index of
the inorganic filler. The temperature coefficient f.sub.A or
f.sub.C of refractive index is given by the formula (3):
wherein n(T.sub.1) is the refractive index of the cured product of
the unfilled composition or the inorganic filler at T.sub.1.degree.
C. and n(T.sub.2) is the refractive index of the cured product of
the unfilled composition or the inorganic filler at T.sub.2.degree.
C., with the proviso that T.sub.1 is lower than T.sub.2. Formula
(2) means that the standard deviation of the temperature
coefficient of the refractive index of the cured product of the
unfilled composition on the basis of the temperature coefficient of
the refractive index of the inorganic filler is less than
1.0.times.10.sup.-5.
The measurement of a refractive index is now described. The
refractive index n.sub.A is measured by furnishing the unfilled
epoxy resin composition, molding and curing the composition under
conventional conditions into a sample as shown in FIG. 1, for
example, and measuring the refractive index thereof. The refractive
index n.sub.C of the inorganic filler is measured by dispersing the
inorganic filler in a solvent mixture of dimethylsulfoxide (n.sub.D
=1.4783 at 25.degree. C.) and 1-chloronaphthalene (n.sub.D =1.6305
at 25.degree. C.) in a weight ratio of inorganic filler/solvent
mixture of 50/50, and determining the refractive index of the
solvent mixture at which the dispersion exhibits a light
transmittance of at least 99.9% at each wavelength of 1600 nm, 900
nm and 600 nm, that refractive index being regarded as the
refractive index of the inorganic filler.
The temperature coefficients f.sub.A and f.sub.C of refractive
indexes are determined from the refractive indexes n.sub.A and
n.sub.C measured at temperatures T.sub.1 and T.sub.2 according to
the above-described procedure. Preferably T.sub.1 is set in the
range of 10 to 50.degree. C., especially 20 to 40.degree. C., and
T.sub.2 is set in the range of 60 to 120.degree. C., especially 80
to 100.degree. C.
The standard deviation of refractive index given by [{2(n.sub.A
.sup.2 +n.sub.C .sup.2)-(n.sub.A +n.sub.C).sup.2 }/2].sup.1/2 is
less than 3.0.times.10.sup.-3, usually 0 to 2.5.times.10.sup.-3,
preferably 0 to 2.2.times.10.sup.-3, more preferably 0 to
1.5.times.10.sup.-3, and most preferably 0 to 0.8.times.10.sup.-3.
If this value is more than 3.0.times.10.sup.-3, the cured product
has a reduced light transmittance, compromising the object of the
invention.
The standard deviation of refractive index's temperature
coefficient given by [{2(f.sub.A.sup.2 +f.sub.C.sup.2)-(f.sub.A
+f.sub.C).sup.2 }/2].sup.1/2 is less than 1.0.times.10.sup.-5,
preferably 0 to 0.9.times.10.sup.-5, more preferably 0 to
0.5.times.10.sup.-5, most preferably 0 to 0.2.times.10.sup.-5. If
this value is more than 1.0.times.10.sup.-5, the cured product,
which is transparent at a certain temperature, lowers its light
transmittance as the temperature changes therefrom, compromising
the object of the invention.
In the epoxy resin composition of the invention, the epoxy resin
(A) is not particularly limited in molecular structure and
molecular weight. An epoxy resin having a low temperature
coefficient of refractive index is preferred when the relationships
of formulae (1) and (2) relating to the refractive index and its
temperature coefficient of the cured product of the unfilled epoxy
resin composition and the inorganic filler are taken into
account.
Illustrative examples of suitable epoxy resins include
bisphenol-type epoxy resins such as bisphenol A epoxy resin,
bisphenol F epoxy resin and bisphenol S epoxy resin, novolac-type
epoxy resins such as phenolic novolac epoxy resin and cresol
novolac epoxy resin, triphenolalkane-type epoxy resins such as
triphenolmethane epoxy resin and triphenolpropane epoxy resin,
phenolaralkyl-type epoxy resins, biphenylaralkyl-type epoxy resins,
stilbene-type epoxy resins, naphthalene-type epoxy resins,
biphenyl-type epoxy resins, cyclopentadiene-type epoxy resins, and
alicyclic epoxy resins. Of these, epoxy resins having at least one
naphthalene ring in a molecule are preferred. Mixtures of
naphthalene type epoxy resins of the following formulae (4) and (5)
are more preferred. With the viscosity of the composition taken
into account, it is recommended that the naphthalene type epoxy
resin of formula (5) account for 90 to 100% by weight, especially
95 to 100% by weight of all the naphthalene type epoxy resins, and
the balance of 0 to 10% by weight, especially 0 to 5% by weight be
the naphthalene type epoxy resin of formula (4). ##STR1##
Herein R.sup.1 is a group represented by ##STR2##
R.sup.2 is independently hydrogen or an alkyl group of 1 to 6
carbon atoms, R.sup.3 is hydrogen or a group represented by
##STR3## ##STR4## k is 1 or 2, m is an integer of 0 to 2, and n is
an integer inclusive of 0, desirably an integer of 0 to 3, and more
desirably 0 or 1.
Naphthalene type epoxy resins of the following general formula (6)
are especially desirable. ##STR5##
Herein n is an integer inclusive of 0, desirably an integer of 0 to
5, and more desirably 0 or 1.
The mixing ratio of epoxy resins is not critical. To reduce the
temperature coefficient of refractive index, it is desirable that
the naphthalene type epoxy resins account for 10 to 100%, more
desirably 25 to 100%, even more desirably 60 to 100% by weight of
all the epoxy resins. If the proportion of naphthalene type epoxy
resins is below the range, cured products can be transparent at
certain temperatures, but opaque at other temperatures.
The curing accelerator (B) used herein is not critical although it
is preferably selected depending on whether or not the curing agent
is used or the type of curing agent if used. Where the epoxy resin
is cured alone (self-polymerization type epoxy resin), relatively
strong basic compounds such as imidazole compounds are desirable.
Where the epoxy resin is cured with curing agents such as acid
anhydrides or phenolic resins (acid anhydride curing type or phenol
curing type epoxy resin), even relatively weak basic compounds such
as organophosphorus compounds are employable as well as imidazole
compounds. Illustrative examples of suitable imidazole compounds
include 2-methylimidazole, 2-ethylimidazole, 4-methylimidazole,
4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole,
2-phenyl-4-hydroxymethylimidazole, 2-ethyl-4-methylimidazole,
1-cyanoethyl-2-methylimidazole,
2-phenyl-4-methyl-5-hydroxymethylimidazole, and
2-phenyl-4,5-dihydroxy-methylimidazole. Organophosphorus compounds
that may be used herein include triorganophosphines such as
triphenylphosphine, tributylphosphine,
tri(p-methylphenyl)phosphine, tri(nonylphenyl)phosphine,
tri(p-toluyl)phosphine, tri(p-methoxyphenyl)phosphine,
tri(p-ethoxyphenyl)phosphine, and
triphenylphosphine-triphenylboran; and organophosphines and
derivatives thereof, for example, quaternary phosphonium salts such
as tetraphenylphosphonium tetraphenylborate. Of these, combinations
of acid anhydride curing agents with imidazole compounds or
organophosphine compounds are desirable because of the transparency
of cured products.
The amount of the curing accelerator added is not critical although
an appropriate amount is about 0.1 to 40 parts by weight per 100
parts by weight of the epoxy resin. Particularly when the epoxy
resin is cured alone, about 1 to 40 parts by weight of the curing
accelerator is used per 100 parts by weight of the epoxy resin.
Where curing agents such as acid anhydrides and phenolic resins are
used, about 0.1 to 20 parts by weight of the curing accelerator is
used per 100 parts by weight of the epoxy resin. An amount of the
curing accelerator below the range may invite losses of humidity
resistance and heat resistance due to undercure. With an amount of
the curing accelerator beyond the range, the composition in uncured
state may become unstable during storage.
Component (C) may be any type of inorganic filler. Suitable fillers
include crystalline or amorphous silica, talc, mica, silicon
nitride, boron nitride and alumina. The only requirement is that
the filler be selected so that the relationships of formulae (1)
and (2) may be met by the refractive indexes of the cured product
of the unfilled composition and the inorganic filler and their
temperature coefficients. Therefore, a filler having a relatively
high refractive index and a low temperature coefficient of
refractive index is desirable. In this sense, it is desirable to
use an amorphous silica-titania co-melt, also known as
silica-titania glass.
The amorphous silica-titania co-melt (i.e., silica-titania glass)
may be prepared by a conventional sol-gel process using an
alkoxysilane and an alkoxytitanium as starting reactants. Then the
refractive index of the inorganic filler can be adjusted in terms
of the blending proportion of reactants. An appropriate blending
proportion of reactants, that is, alkoxysilane/alkoxytitanium is in
the range from 99/1 to 50/50, especially from 90/10 to 70/30 in
molar ratio. If the blending proportion of reactants is outside the
range, the refractive index of the inorganic filler may largely
differ from that of the cured product of the unfilled composition,
resulting in the cured product of the filled composition becoming
opaque.
The shape and particle size of amorphous silica-titania co-melt are
not critical and may be selected in accordance with a particular
application. For use as an underfill for flip-chip type
semiconductor devices, for example, the preferred co-melt has an
irregular shape with no acute corners or spherical shape as well as
an average particle size at most about one-tenth as large and a
maximum particle size at most one-half as large as the gap between
the substrate and chip in a flip-chip semiconductor device.
Specifically, the average particle size is usually up to 10 .mu.m,
preferably 0.5 to 10 .mu.m, more preferably 1 to 5 .mu.m and the
maximum particle size is up to 50 .mu.m, preferably up to 25 .mu.m,
and more preferably up to 12 .mu.m. The average particle size may
be suitably determined as the weight average value or median
diameter, for example, by laser diffraction analysis.
The amount of amorphous silica-titania co-melt added is not
critical although it is desirable from the requirement of formulae
(1) and (2) for the co-melt to account for 10% to 100% by weight,
more preferably 30% to 100% by weight, and most preferably 50% to
100% by weight of all inorganic fillers. If the amount of amorphous
silica-titania co-melt added is below the range, cured products may
become opaque. The addition amount of all inorganic fillers
including the amorphous silica-titania co-melt is preferably about
50 to 1,000 parts, especially about 100 to 500 parts by weight per
100 parts by weight of the total of other components. If the amount
of inorganic filler added is below the range, cured products may
lose, in part, heat resistance, humidity resistance and low stress
property. An excessive amount of inorganic filler may provide an
uncured composition with an extremely increased viscosity,
compromising the working efficiency.
In the epoxy resin composition of the invention, a curing agent may
be added as component (D). Illustrative of the curing agent are
acid anhydrides, phenolic resins, and amine compounds, with the
acid anhydrides being desirable for the transparency of cured
products. The type of the acid anhydride is not critical although
preferred acid anhydrides include aliphatic acid anhydrides such as
dodecenylsuccinic anhydride, polyadipic anhydride, polyazelaic
anhydride and polysebacic anhydride; alicyclic acid anhydrides such
as methyltetrahydrophthalic anhydride, methylhexahydrophthalic
anhydride, hymic anhydride, hexahydrophthalic anhydride,
tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride
and methylcyclohexane dicarboxylic anhydride.
The amount of acid anhydride blended is not critical although an
appropriate amount is to give an epoxy resin/acid anhydride ratio
between 100/50 and 100/200, and especially between 100/80 and
100/125 in equivalent ratio. An amount of the acid anhydride
outside the range can sometimes cause undercure, resulting in
losses of humidity resistance and heat resistance.
In the epoxy resin composition, other additives such as flame
retardants, coupling agents and thermoplastic resins may be blended
insofar as they do not compromise the objects of the invention.
When the epoxy resin composition of the invention is prepared, the
respective components may be blended in any desired order and mixed
in any desired way. For example, a pre-blend of the components is
mixed in a two-roll mill, three-roll mill, kneader or mixer of any
desired type while heating if desired.
The epoxy resin composition is obtained in a solid or liquid state.
In the solid state, it is used in the form of granules, tablets or
film. In the liquid state, it is used as being filled in a suitable
container such as a syringe. The epoxy resin composition is usually
cured by heating at a temperature of about 100 to 150.degree. C.
for about 1 to 6 hours.
Since the epoxy resin composition cures into a product which
exhibits and maintains high transparency in various temperature
environments, it is best suited for use with optical semiconductor
devices. Typical applications include sealants for light emitting
and receiving devices and interfacial adhesives for optical
communication ICs and LSIs.
EXAMPLE
Examples of the invention and comparative examples are given below
by way of illustration, and are not intended to limit the
invention.
Example 1-3 and Comparative Examples 1-2
Epoxy resin compositions were prepared by blending epoxy resins A
and B, a curing accelerator (2E4MZ: 2-ethyl-4-methylimidazole),
inorganic fillers A to D (amorphous silica-titania co-melt obtained
by a sol-gel process) shown in Table 1, and a curing agent (4MTHPA:
4-methyltetrahydrophthalic anhydride) according to the formulation
shown in Table 2, followed by intimate mixing.
Each epoxy resin composition was cured under conditions:
100.degree. C./1 hour plus 150.degree. C./4 hours into a test
sample of 10 mm.times.50 mm.times.0.1 mm (optical path length) as
shown in FIG. 1.
Separately, a semiconductor device as shown in FIG. 2 was prepared
by coating each epoxy resin composition on a BT substrate 1 as a
coating 2 of 10 mm.times.10 mm.times.0.1 mm, on which a silicon
chip 3 of 10 mm.times.10 mm.times.0.3 mm was placed. The
composition was cured under conditions: 100.degree. C./1 hour plus
150.degree. C./4 hours, completing the device.
These epoxy resin compositions were examined by the following tests
(a) to (d). The results are shown in Table 2.
(a) Refractive index and Temperature Coefficient
For the cured products of unfilled epoxy resin compositions, test
samples as shown in FIG. 1 were prepared under the same conditions
as used for the cured products of the filled epoxy resin
compositions. These samples were measured for refractive index
n.sub.A . The refractive index n.sub.C of an inorganic filler was
measured by dispersing the inorganic filler in a solvent mixture of
dimethylsulfoxide (n.sub.D =1.4783 at 25.degree. C.) and
1-chloronaphthalene (n.sub.D =1.6305 at 25.degree. C.) in a weight
ratio of inorganic filler/solvent mixture of 50/50, and determining
the refractive index n.sub.C of the solvent mixture when the
dispersion exhibited a light transmittance of at least 99.9% at
each wavelength of 1600 nm, 900 nm and 600 nm. Measurements were
made at 25.degree. C. (=T.sub.1) and 100.degree. C. (=T.sub.2). It
is noted that the mixing ratio of solvents in the solvent mixture
was not fixed. Instead, a number of solvent mixtures having
different mixing ratios were furnished, the inorganic filler was
dispersed therein, the dispersed systems were observed for
transparency, and the refractive index of the solvent mixture from
which a transparent system was obtained was regarded as the
refractive index of the inorganic filler. From the refractive
indexes n.sub.A and n.sub.C at 25.degree. C. (=T.sub.1) and
100.degree. C. (=T.sub.2), their temperature coefficients f.sub.A
and f.sub.C were calculated according to formula (3).
(b) Light Transmittance
The test sample of FIG. 1 was measured for light transmittance at a
wavelength of 1600 nm, 900 nm and 600 nm and a temperature of
25.degree. C. and 100.degree. C.
(c) Solder Crack Resistance after Moisture Absorption
A semiconductor device as shown in FIG. 2 was allowed to stand for
24 hours in an atmosphere of 121.degree. C., RH 100% and 2 atm. It
was immersed for 10 seconds in a solder bath at 240.degree. C. The
number of cracked samples per the total number of tested samples is
reported.
(d) Thermal Cycling Test
A semiconductor device as shown in FIG. 2 was immersed for 10
seconds in a solder bath at 240.degree. C. and then for 10 seconds
in liquid nitrogen. The number of cracked samples after ten cycles
per the total number of tested samples is reported.
Epoxy resin A: epoxy equivalent 141 ##STR6## n=0.046
Epoxy resin B: epoxy equivalent 172 ##STR7## n=0.014
TABLE 1 Blending ratio Average Maximum Inorganic (mol %) particle
size particle size filler SiO.sub.2 TiO.sub.2 (.mu.m) (.mu.m) A 85
15 4.5 .ltoreq.12 B 86 14 3.8 .ltoreq.12 C 87 13 4.8 .ltoreq.12 D
88 12 4.2 .ltoreq.12
TABLE 2 Comparative Composition Example Example (pbw) 1 2 3 1 2
Epoxy resin A 62.6 40.1 18.9 0 62.6 Epoxy resin B 0 24.1 46.8 67.2
0 2E4MZ 1 1 1 1 1 Inorganic filler A 100 0 0 0 0 Inorganic filler B
0 100 0 0 0 Inorganic filler C 0 0 100 0 0 Inorganic filler D 0 0 0
100 0 4MTHPA 37.4 35.8 34.3 32.8 37.4 (a) Refractive index n.sub.A
1.545 1.541 1.538 1.535 1.545 n.sub.C 1.544 1.539 1.535 1.530 --
formula (1) 0.707 1.414 2.121 3.536 -- (.times.10.sup.-3) (a)
Temperature coefficient f.sub.A (.times.10.sup.-5) 6.1 6.9 7.7 8.6
6.1 f.sub.C (.times.10.sup.-5) 6.0 6.2 6.5 6.7 -- formula (2) 0.07
0.49 0.85 1.34 -- (.times.10.sup.-5) (b) Transmittance at 25
.degree. C. 1600 nm 100 100 100 100 100 900 nm 100 100 100 100 100
600 nm 100 99 99 98 100 (b) Transmittance at 100.degree. C. 1600 nm
100 100 100 95 100 900 nm 100 98 97 80 100 600 nm 100 96 95 70 100
(c) Solder crack 0/20 0/20 0/20 0/20 20/20 resistance (d) Thermal
cycling test 0/20 0/20 0/20 0/20 20/20 Note: formula (1) =
[{2(n.sub.A.sup.2 + n.sub.C.sup.2) - (n.sub.A + n.sub.C).sup.2 } /
2].sup.1/2 formula (2) = [{2(f.sub.A.sup.2 + f.sub.C.sup.2) -
(f.sub.A + f.sub.C).sup.2 } / 2].sup.1/2
There has been described an epoxy resin composition which in the
cured state maintains high transparency in various temperature
environments and has improved heat resistance, humidity resistance
and low stress property. When the composition is used in sealing of
optical semiconductor devices, typically as sealants for light
emitting and receiving devices and interfacial adhesives for
optical communication ICs and LSIs, excellent performance is
exerted in differing temperature environments.
Japanese Patent Application No. 2000-277405 is incorporated herein
by reference.
Although some preferred embodiments have been described, many
modifications and variations may be made thereto in light of the
above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
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